1. Field of the Invention
The present invention relates to an idling engine speed controlling apparatus for an engine wherein a quantity of intake air supplied to the engine is corrected on the basis of an electric load.
2. Discussion of Background
A conventional idling engine speed controlling apparatus for an engine is disclosed in, for instance, Japanese Unexamined Patent Publication 5855/1980.
The apparatus disclosed in the publication is such that a generator is driven by an engine to charge a battery by the output of the generator; when a terminal voltage at the battery is lower than a reference value, a switching means is actuated to close a circuit extending from the battery to the field winding, and at the same time, a current is supplied to the field winding to continue generation of electric power so that the battery is charged.
Further, it is so adapted that pulses are generated by a pulse signal generating means so as to correspond to opening and closing operations by the switching means, a current is caused to flow to the field winding on the basis of the pulse signals, and when a time for flowing the current is longer than a predetermined time, a degree of opening of throttle valve disposed in the air passage of a carburetor is increased by a predetermined quantity. Namely, an amount of air supplied to the engine is controlled depending on errors between a target idling engine speed and an actual engine speed so that the engine revolution speed is kept to be a target speed.
In the conventional engine speed controlling apparatus having the construction described above, when an electric load such as a headlamp, an electric radiator fan and so on which are connected to a battery and consume a large amount of electric power is used, the load to the generator becomes large, whereby the engine revolution number is decreased. The decreased engine revolution number is restored to a normal revolution number by the above-mentioned control. However, since a response of control was slow in the conventional controlling apparatus, an engine stall sometimes takes place when an electric load was large.
In order to eliminate the above-mentioned problem, there has been proposed a method of correcting a quantity of intake air by detecting a plurality of switches of electric load as disclosed in, for instance, Japanese Unexamined Patent Publication 197449/1983. However, this method requires a switch and an input circuit corresponding to the number of electric load, hence it results in a complicated structure of the control apparatus.